Process for the production of γ-butyrolactone

ABSTRACT

A process for the liquid-phase hydrogenation of maleic anhydride to γ-butyrolactone in the presence of a catalyst composed of cobalt oxide and palladium on a support of silica.

BACKGROUND OF THE INVENTION

The invention relates to a process for the production of a novelcatalyst and to the hydrogenation of maleic anhydride in the liquidphase at an elevated pressure and temperature to produce γ-butyrolactoneemploying said catalyst.

Catalysts of multifarious compositions are available for thehydrogenation of maleic anhydride to γ-butyrolactone, Raney catalystsbeing the best known catalysts. However as taught by U.S. Pat. No.2,772,292, Raney catalysts are highly pyrophoric and cannot beregenerated so that it has become increasingly the practice to usesupported catalysts. The supported catalysts contain nickel as thecatalytic component or cobalt in combination with a promoter, forexample molybdenum or rhenium. While these supported catalysts are alsopyrophoric, they can be stabilized by treatment with air diluted withcarbon dioxide or a protective gas. The stabilizing treatment is,however, cumbersome and expensive. The supported catalysts have theadditional disadvantage that their selectivity for γ-butyrolactone isnot as high as would be desirable such that C₃ and C₄ alcohols and acidsand their products of esterification are formed as by-products. The highby-product formation results in a reduced yield of γ-butyrolactone andthe catalyst is irreversibly deactivated by the acids.

It is an object of the invention to provide a process for thehydrogenation of maleic anhydride to γ-butyrolactone in the liquid phasein high yields.

Another object of this invention is to provide a process for convertingmaleic anhydride to γ-butyrolactone in the presence of a novel selectiveand non-pyrophoric catalyst which does not require stabilization.

Yet another object of this invention is to provide a method forpreparing a new catalyst useful in converting maleic ahydride toγ-butyrolactone where the catalyst is readily regenerable.

Other objects and advantages will become apparent from a reading of thefollowing detailed description and examples.

DESCRIPTION OF THE INVENTION

Broadly, this invention contemplates a process for converting maleicanhydride to γ-butyrolactone which comprises contacting said anhydridein the liquid phase with hydrogen in the presence of a catalyst composedof cobalt oxide and palladium on a support of silica. In general, theprocess is conducted under elevated pressures and at elevatedtemperatures as for example temperatures in the range of from 20° to400° C., preferably from 100 to 250° C. and under pressures suitably offrom 50 to 350 kg/cm², preferably 100 to 150 kg/cm².

The novel catalyst of this invention comprises from 20 to 30 weightpercent cobalt oxide, 0.5 to 1.0 weight percent palladium on a silicasupport. The catalyst provided herein is non-pyrophoric and is preparedby impregnating a silica support with at least one solution of adecomposable salt of a catalytically active metal, drying theimpregnated support, heating the impregnated support in air or in anitrogen containing environment and decomposing the salt, and activatingthe catalyst in a hydrogen environment. More specifically, the method ofpreparing the catalyst is characterized by the following steps:

a. impregnating a silica support with a cobalt salt solution and dryingsaid cobalt impregnated silica;

b. impregnating said dried cobalt impregnated silica support of (a) withpalladium and drying said cobalt-palladium impregnated silica;

c. calcining said dried impregnated silica support of (b) at atemperature sufficient to decompose said cobalt salt to cobalt oxide;and

d. activating said calcined support of (c) at a temperature of 400° to500° C., preferably 420° to 480° C. in a hydrogen atmosphere.

It has surprisingly been found that a highly active cobalt catalystwhich is non-pyrophoric, may be obtained if the support is dried afterits impregnation with the cobalt salt solution, and is only thenimpregnated with palladium. However, if the silica support isimpregnated simultaneously with the cobalt salt solution and palladiumor with one solution after the other without intermediate drying, acatalyst is obtained which is pyrophoric. The essential feature of theinvention thus resides in the observation of a specific order ofsuccession in which the solutions of the catalytically active metals areapplied, and the drying between the applications of the cobalt saltsolution and of the palladium. It has been found that the combination ofcobalt and palladium has a synergistic effect. Moreover, since thecatalysts of this invention are not pyrophoric, stabilization of thesame is entirely superfluous.

Commercially available kieselguhr or commercially available SiO₂ in theform of granules or pellets having an average diameter of about 1.5 to3.5 mm., preferably from 2 to 3 mm. may serve as the SiO₂ support. Anysuch pre-formed SiO₂ used should be degassed and dried in vacuo at anelevated temperature before it is impregnated with the cobalt saltsolution. Fifteen minutes drying at 80°-90° C. is generally sufficient.

The cobalt salt solution is a solution of a cobalt salt which isdecomposable when heated, for example the nitrate, the formate, theacetate or the salt of another volatile organic acid.

The palladium can also be introduced in the form of a solution of a saltwhich is decomposable by reduction; palladium chloride is the leastexpensive and is thus the preferred salt. The palladium may also beintroduced in the form of palladium on carbon (10% by weight ofpalladium deposited on 90% by weight of activated carbon) which is thenadmixed with the supporting material impregnated with cobalt.

The SiO₂ support, the cobalt salt solution and the palladium, that is tosay, the palladium salt solution or palladium deposited on activatedcarbon, are used in amounts sufficient to produce a catalyst of thefollowing average composition:

from 20 to 30% by weight of CoO

from 0.5 to 1% by weight of Pd,

the balance bringing the total to 100% by weight being SiO₂.

Solutions of the highest possible concentration, that is to say,solutions ensuring a good impregnation facilitating thorough kneading ofthe mass are preferably used. Higher dilutions, while having nodetrimental effect upon the activity of the catalyst, necessitate,however, a prolonged drying, whilst the use of highly concentratedsolutions involves extended mixing periods. A little water is addedwhere palladium deposited on activated carbon is used so that akneadable mass may be obtained.

The drying after the impregnation with the cobalt salt solution may becarried out at a temperature up to 110° C. under atmospheric pressure orin vacuo at correspondingly lower temperatures. It has been found thatthe best results are obtained when the drying step is carried out at atemperature of about 80° C. within about one hour in a vacuum of 14Torr.

In accordance with the invention, the second metallic component of thecatalyst, namely the palladium, is incorporated in the SiO₂ supportladen with Co after the drying step by admixing a palladium saltsolution or palladium deposited on carbon and a small amount of water inthe manner hereinbefore described. The mass so obtained is thenthoroughly kneaded during which the palladium component is absorbed onthe surface of the catalyst impregnated with cobalt salt. This isfollowed by drying in vacuo at about 100° to 120° C., suitably 110° C.,for a few hours, for example for one day, preferably for from 10 to 12hours, and, finally, decomposition of the cobalt salt and of thepalladium salt when employed by thermal treatment in air or nitrogen andsubsequent activation of the crude catalyst by heating in a hydrogenatmosphere. In the process according to the invention, the decompositionis carried out at a temperature of 400° to 500° C., preferably 420° to480° C., for 1.5 - 5 hours and in a highly preferred embodiment at 450°C. for 3 hours, at a rate of flow of the nitrogen of from 2 to 30liters, preferably 25 liters, per hour. The activation of the catalystis carried out at a temperature of from 400° to 500° C., preferably 420°to 480° C., for a period of from 1.5 to 5 hours and in a highlypreferred embodiment at 450° C. for a period of 3 hours, at a rate offlow of the hydrogen of from 20 to 30 liters, preferably at a rate of 25liters, per hour. It will be understood that the rates of flow of thegas most suitable at the time depend upon the conditions under which thetreatments are carried out, such as the depth of layer or the movementof the catalyst, the size of the batch, the size of the vessel, and thelike.

The catalyst obtained by the process according to the invention isdistinguished by the fact that it is non-pyrophoric and need not besubjected to a special stabilizing treatment. It is obtained in the formof a black, loose powder, or in the form of lustrous, black globules orgranules according to the form of the SiO₂ support charged. The catalystis particularly suitable for the hydrogenation of maleic acid anhydrideto γ-butyrolactone in the liquid phase. The hereinafter given Examples 5to 8 and Table II connected therewith show that a 100% conversion ofmaleic anhydride is obtained with a very high yield of γ-butyrolactone.The pulverulent catalyst is predominantly suitable for batchwiseoperation, catalysts in spherical form being advantageously used forcontinuous operation by reason of their high mechanical stability.

The catalyst according to the invention has a very long useful life. Ithas still its full activity even after 1000 hours of continuousoperation. The catalyst may, moreover, be very easily regenerated bypassing air over it followed by a treatment with hydrogen.

According to a preferred embodiment of the process of this invention,hydrogen is introduced to a reactor containing maleic anhydride at apressure of from 100 to 150 kg/cm², the temperature is raised to 100° to250° C. within 2 hours, and subsequently the reaction is allowed tocontinue for 2 more hours. Shorter or longer perods of time can also beemployed. While the amount of catalyst employed in the reaction can varyover a broad range, we employ from about 0.1 to 100, preferably about 5to 20, parts by weight of the cobalt oxide-palladium on silica catalystper 100 parts by weight of maleic anhydride. In contrast to otherprocesses for converting maleic anhydride to γ-butyrolactone which areconducted in the gaseous phase, the process of our invention is carriedout in the liquid phase which is a great advantage with regard toconversion and reactor dimensions. The catalytic process can beconducted in a wide range of solvents inert to the reaction as, forexample, aliphatic alcohols such as methanol, ethanol, butanol andhigher alcohols; aromatics such as benzene, toluene or xylene;dimethylformamide; and cyclic ethers such as tetrahydrofuran ortetrahydropyran. A particularly preferred solvent for converting maleicanhydride is γ-butyrolactone which is the compound that emerges as theend product of the process and this need not be removed. Whetherγ-butyrolactone or another solvent is used in the course of thereaction, the results are the same. In general, the maleic anhydrideconcentration in the solvent can vary from 25 to 75 weight percent. Whenγ-butyrolactone is employed as solvent about 50 percent solutions aremost convenient. In the instance where γ-butyrolactone is intended to beconverted to tetrahydrofuran in a further stage, the reaction solventfor the maleic anhydride in such a case is preferably tetrahydrofuran.

The product of the instant process, γ-butyrolactone, has utility as asolvent and as a thinner for paints and lacquers. In addition,γ-butyrolactone is useful as an intermediate in the production oftetrahydrofuran.

The invention and the advantages obtained thereby are illustrated in thefollowing Examples.

EXAMPLES 1 to 4

In these Examples catalysts according to the invention in pulverulentform were produced.

Commercially available kieselguhr was impregnated with a cobalt nitratesolution and the water was evaporated in vacuo. A palladium chloridesolution or palladium deposited on activated carbon was then added, themass was kneaded and thus thoroughly mixed and subsequently dried invacuo at 110° for 10 hours followed by grinding the lumpy material to afine powder. The powder so obtained was heated for three hours in acurrent of nitrogen (rate of flow 25 liters per hour) to a temperatureof 450° C. to decompose the nitrate, and the crude catalyst wasactivated for 3 hours in a hydrogen current (rate of flow: 25 liters perhour) at the same temperature.

The quantities in which the individual starting materials were used inthe different Examples are shown in Table I.

In all of the four Examples, the catalysts were obtained in the form ofa loose, non-pyrophoric, black powder.

EXAMPLES 5 to 7

In these Examples the catalysts according to the invention were obtainedin the form of small spheres or pellets.

Commercially available SIO₂ spherical pellets from 2 to 3 mm. indiameter, were dried in vacuo at a temperature of 80° C. for 15 minutes.This was followed by impregnation with a cobalt nitrate solution andevaporation of the water in vacuo. A palladium chloride solution wasthen added followed by thorough mixing and drying in vacuo at 110° C.for 10 hours. The decomposition of the nitrate and the activation of thecrude catalyst were carried out as described in Examples 1 to 4. Thequantities in which the individual starting materials in Examples 5 to 7were used are also shown in Table I.

In all of the three Examples, the catalysts were obtained in the form oflustrous, black non-pyrophoric spheres or pellets.

                                      TABLE 1                                     __________________________________________________________________________    Production of the catalysts in Examples 1 to 7                                Catalyst according                                                            to Example No.                                                                          SiO.sub.2 Co(NO.sub.3).sub.2 . 6 H.sub.2 O                                                         PdCl.sub.2     Pd/C                            __________________________________________________________________________    1         Kieselguhr, 79g                                                                         77.6g      1.67g in 100 ml 1n HNO.sub.3                                                                 --                              2         Kieselguhr, 70g                                                                         77.6g in 100 ml.                                                                         --             10Pd on activate                                    H.sub.2 O                 carbon (10%)                    3         Kieselguhr, 74g                                                                         97.1g      6.67g (containing 15% Pd)                                                                    --                                                             in 50 ml. H.sub.2 O                            4         Kieselguhr, 69g                                                                         116.6g     "              --                              5         Spherical pellets                                                                       388g in 300 ml.                                                                          16.7g (containing 15% Pd)                                                                    --                                        2-3 mm 395g          in 200 ml. H.sub.2 O                           6         2-3 mm 124.5g                                                                           121.2g in 100 ml.                                                                        7.9g (containing 15% Pd)                                                                     --                                                  H.sub.2 O  in 50 ml. H.sub.2 O                            7         2-3 mm 603g                                                                             788g in 750 ml.                                                                          53.6g (containing 15% Pd)                                                                    ---        H.sub.2 O in 500                                                             ml. H.sub.2           __________________________________________________________________________                                                            O                      The catalysts obtained in Examples 1 to 7 were tested in nine tests     (Examples 8 to 16 ) for their suitability as catalysts for the     hydrogenation of maleic anhydride to γ-butyrolactone.

EXAMPLES 8 to 15

An autoclave provided with a stirrer, a gas inlet tube and a gas outlettube was charged with the maleic anhydride to be hydrogenated, thesolvent γ-butyrolactone and the catalyst. The autoclave was thenflushed, twice with nitrogen and once with hydrogen, and was then closedand heated to 100° C. When this temperature was reached, hydrogen at 150atmospheres pressure was placed in communication with the autoclave.When a constant pressure was reached in the autoclave, the temperaturewas increased to 250° C. and fresh hydrogen at 150 atmospheres pressurewas again added until a constant pressure was reached again.

After removal of the excess pressure, the product was separated from thecatalyst and subjected to gas chromatographic analysis with reference todiethyl ketone as a standard.

The following Table II gives particulars of the individual Examples,including the quantities of maleic anhydride and of solventγ-butyrolactone used, and the catalyst quantity of it used in each case.The results of the analysis of the product are also shown in Table II.

                                      TABLE II                                    __________________________________________________________________________    Hydrogenation of maleic anhydride to γ-butyrolactone using              the catalysts produced in Examples 1 to 6                                     __________________________________________________________________________                                 Composition of the                                                            hydrogenation product                            Catalyst                     wt. %                                                               Quantity of MSA               MSA   GBL                    Example                                                                            Example                                                                            Quantity charged                       conversion                                                                          selectivity            No.  No.  grams    g/g GBL   THF GBL BSE H.sub.2 O                                                                         Others                                                                            %     %                      __________________________________________________________________________     8   1    20       200/200   3.2 86.2    8.1 2.5 100   88.5                    9   1    40       200/200   4.1 86.3                                                                              0.2 8.7 0.7 100   88.7                   10   2    30       300/300   3.1 85.6    8.3 3.0 100   87.0                   11   3    20       200/200   5.2 84.1                                                                              1.8 8.6 0.3 100   83.5                   12   4    20       200/200   4.0 86.4                                                                              0.8 8.0 0.8 100   89.0                   13   5    20       200/200   0.7 88.0    7.9 3.0 100   92.6                   14   6    20       200/200   4.1 86.5                                                                              0.2 9.2 0   100   89.3                   15   6    27 + 3 g Pd/C                                                                          300/300   2.2 88.2                                                                              0.5 8.6 0.5 100   93.2                             (5% Pd)                                                             __________________________________________________________________________     MSA maleic anhydride                                                                            BSE   butyric acid                                         GBL  γ -butyrolactone                                                                      H.sub.2 O                                                                           water formed during the reaction                     THF  tetrahydrofuran                                                                             "Others"                                                                            constituents not analysed                        

EXAMPLES 16 to 18

The conditions under which these Examples were carried out were similarto those used in Examples 8 to 15 except that tetrahydrofuran instead ofγ-butyrolactone served as the solvent.

Particulars of the three Examples and the results obtained are shown inTable III.

                                      TABLE III                                   __________________________________________________________________________    Hydrogenation of maleic anhydride to gamma-butyrolactone using                the catalysts produced according to Examples 1, 2 and 7                       __________________________________________________________________________                             Composition of the                                                            hydrogenation product                                Catalyst                 Wt. %                                                               Quantity of MSA               MSA   GBL                        Example                                                                            Example                                                                            Quantity                                                                           charged                       conversion                                                                          selectivity                No.  No.  grams                                                                              g/g THF   THF BSE GBL H.sub.2 O                                                                         Others                                                                            %     %                          __________________________________________________________________________    16   1    20   200/200   50.8                                                                              1.5 38.7                                                                              8.0 1.0 100   90.8                       17   2    20   200/200   49.9                                                                              0.5 40.9                                                                              8.0 0.7 99    96.2                       18   7    20   200/200   49.2                                                                              0.9 40.1                                                                              8.3 1.5 100   94.0                       __________________________________________________________________________

In the following Examples of Comparison A and B, a cobalt catalyst and apalladium catalyst, respectively, were prepared and their suitabilityfor converting maleic anhydride to γ-butyrolactone was tested.

EXAMPLE OF COMPARISON A

A catalyst was prepared from 80 grams of kieselguhr and 77.6 grams ofcobalt chloride-hexahydrate, as described in Examples 1 to 4, with theexception of the addition of palladium chloride solution or of palladiumdeposited on activated carbon.

200 Grams of maleic anhydride and 200 grams of γ-butyrolactone werehydrogenated at a temperature of 250° C and at a hydrogen pressure of150 atmospheres in the presence of 20 grams of the catalyst describedabove until a constant pressure was reached (as described in Examples 8to 15 ).

The hydrogenation product had the following composition (in percent byweight):

    ______________________________________                                        THF                   0.9                                                     GBL                   62.3                                                    BSE                   0.5                                                     H.sub.2 O             7.0                                                     others                29.3                                                    MSA conversion        100                                                     GBL selectivity       32.4                                                    ______________________________________                                    

EXAMPLE OF COMPARISON B

200 Grams of maleic anhydride in 200 grams of γ-butyrolactone werehydrogenated in the presence of 20 grams of a commercially availablepalladium/kieselguhr catalyst (10 per cent by weight of Pd), asdescribed in Example A.

The hydrogenation product comprises the following composition (in percent by weight):

    ______________________________________                                        THF                   0.1                                                     GBL                   60.9                                                    BSE                   1.8                                                     H.sub.2 O             3.0                                                     others                34.2                                                    MSA conversion        100                                                     GBL selectivity       32.4                                                    ______________________________________                                    

In comparing the Examples 8 to 15 with the Examples of Comparison A andB with respect to the γ-butyrolactone in the hydrogenation products andthe Examples 8 to 17 with the Examples of Comparison A and B withrespect to the selectivity of γ-butyrolactone, the synergistic effect ofthe combination of cobalt and palladium showed clearly.

We claim:
 1. A process for converting maleic anhydride toγ-butyrolactone which comprises contacting said anhydride in the liquidphase with hydrogen at a temperature of from about 20° to 400° C. and apressure of from about 50 to 300 kg/cm² in the presence of a catalystcomprising cobalt oxide and palladium on silica, wherein said catalystcomprises from about 20 to 30 weight percent cobalt oxide and from 0.5to 1.0 weight percent palladium on a silica support.
 2. A processaccording to claim 1 wherein said contacting is conducted at atemperature of from about 100° to 250° C. and a pressure of from about100 to 150 kg/cm².
 3. A process according to claim 1 wherein saidtreating is conducted in an inert solvent.
 4. A process according toclaim 3 wherein said solvent is γ-butyrolactone.
 5. A process accordingto claim 3 wherein said solvent is tetrahydrofuran.